Bush was seen as weak among moderates and crucial independents, while Portman was viewed as risky by the party's right, an ABC News-Washington Post poll about potential vice presidential candidates for presumptive GOP presidential nominee Mitt Romney released Friday said.
Another potential candidate, Sen. Marco Rubio of Florida, received more positive than negative responses among his Hispanics, even though a third of the respondents said they were undecided.
Those surveyed expressed an unfavorable rather than favorable opinion about Bush, 45 percent to 36 percent, results indicated. By a 30 percent-to-19 percent margin, respondents said the same of Portman.
U.S. residents had a 32 percent-to-29 percent, favorable-unfavorable view of Rubio, results indicated.
Portman and Rubio have room to change people's minds, pollsters said, because large numbers -- 51 percent for Portman and 39 percent for Rubio -- said they had no opinion.
Nineteen percent said they had no opinion about Bush, the son and brother of the country's 41st and 43rd presidents.
Results are based on nationwide telephone interviews with 1,009 adults conducted May 30-June 3. The margin of sampling error is 3.5 percentage points.